Piston carried detonation suppression means for internal combustion engines



July 3, 1956 A. G. BODINE, JR 2,752,908

PESTON CARRIED DETON IQN SUPPRESSION MEANS FOR INTERNAL BUSTXON ENGINESOriginal Filed July 2, 195 2 Sheets-Sheet l FIG.|

0000 O O O 0000 FIG. 2 28 INVENTOR.

ALBERT G. BODINE JR.

July 3, 1956 A. 5. BODINE, JR 2,752,908 PISTON CARRIED DETONATIONSUPPRESSION MEANS FOR INTERNAL COMBUSTION ENGINES Original Filed July 2,1954 2 Sheets-Sheet 2 FIGS 35 35 35 FIG. 4

INVENTOR.

ALBERT G. BODINE JR.

ATTORNEY PISTON CARRIED DETGNATION SUPPRESSION MEANS FOR lNTERNALCOMBUSTION EN- GENES Albert G. Bodine, lira, Van Nuys, Calif.

Application Uctoher 24-, 1951, Serial No. 252,818, which is a divisionof application Serial No. 234,688, July 2, 1951, now Patent No.2,573,536, dated October 30, 1951. Divided and this application December6, 1955', Serial No. 551,263

3 Claims. (Cl. 123191) This invention relates generally to internalcombustion engines and to means for suppressing irregular burning anddetonation of fuel-air mixture therein. The invention is based on mydiscovery that detonation in combustion engines involves acousticphenomena and can be alleviated by means of certain acoustic apparatusused in combination with the combustion chamber.

The present application is a division of my copending application Ser.No. 252,818, filed October 24, 1951, entitled Engine Detonation Controlby Acoustic Methods and Apparatus which was a division of my earlierapplication Ser. No. 234,688, filed July 2, 1951, entitled EngineDetonation Control by Acoustic Methods and Apparatus (now Patent No.2,573,536), which last mentioned case was in turn a continuation-in-partof my prior application Ser. No. 760,914, filed July 14, 1947, entitledMethod and Means for Suppressing Detonation in Internal CombustionEngines, now abandoned. Reference is also made to the followingapplications filed as divisions hereof: Detonation Spoilers for internalCombustion Engines, Ser. No. 578,472, filed April 16, 1956; Horn TypeDetonation Attenuation Means for Internal Combustion Engines, Ser. No.578,473, filed April 16, 1956; Self- Cleaning Detonation AttenuationMeans for Internal Combustion Engines, Ser. No. 578,474, filed April 16,195 6 Helmholtz Resonator Detonation Attenuation Means for InternalCombustion Engines, Ser. No. 578,475, filed April 16, 1956; andDetonation Suppression Helmholtz Resonators for internal CombustionEngines, Ser. No. 578,476.

The present invention is based on the fact that detonation in an enginecombustion chamber produces sound waves, a large part of which rise tohigh amplitude at resonant frequencies of the chamber, and On mydiscovery that the sound waves produce the various wellknown and harmfulmanifestations of detonation. According to my basic invention, 1 inhibitor attenuate these harmful effects by interfering with or attenuatingthe high amplitude detonation-induced sound waves, and this is done byuse in connection with the combustion chamber of acoustic attenuationmeans made responsive to the frequencies at which the detonation inducedsound waves build up to high amplitudes.

The acoustic detonation attenuation means of the present invention iscapable of being used in either the combustion chamber head wall or inthe head wall of the piston, but comprises configurations particularlywel1- adapted for incorporation in the head Wall of the piston. Variousdisclosed embodiments of the invention hence have in common theadvantage of susceptibility to piston mounting, and hence the commonadvantage that they may be incorporated in conventional engines withoutmodification of the combustion chamber head wall, and require onlysubstitution of pistons provided with the special acoustic attenuatorconfigurations of the invention.

A general object of the invention is the provision of dtatcs Patent2,752,908 i atented July 3, 1956 simple and effective acousticattenuator means for the combustion chambers of internal combustionengines, particularly, if not necessarily, adapted for incorporation inthe head of the piston of the engine.

Further objects are concerned with simple attenuator configurations ofsubstantial effectiveness, simplicity and low cost.

The acoustic attenuators of the invention will be best understood byreferring immediately to the following detailed description of severalillustrative embodiments thereof, reference for this purpose being hadto the accompanying drawings, in which:

Fig. l is a vertical transverse section through an internal combustionengine showing certain detonation sound wave attenuator configurationsin accordance with the invention;

Fig. 2 is a top plane view of a portion of an engine piston equippedwith a form of the present invention;

Fig. 3 is a detailed section taken on line 3--3 of Fig. 2;

Fig. 4 is a vertical medial section through the upper portion of apiston showing another embodiment of the invention;

Fig. 5 is a vertical detailed section through a portion of the top endof a piston showing another form of the invention;

Fig. 6 is a view similar to Fig. 5 showing another form of theinvention;

Fig. 7 is a fragmentary vertical section through a piston showinganother form of the invention; and

Fig. 8 shows a piston, partly in elevation and partly in section,showing still another form of the invention.

With reference first to Fig, 1, there is shown an illustrative L.--headengine comprised of a water-cooled block 11 a water-cooled head 11fastened to block 10, a piston 14 working in cylinder 15 in block 10, anexhaust valve 16, and a spark plug 17. It will be understood that anintake valve (not shown) will be located along-side exhaust valve 16,such valve being understood to be in front of the plane of the drawing.Block 10 and head 11 are shown with more or less conventional coolingjackets, and head 11 has an inner combustion chamber Wall 20, enclosinga combustion chamber space 21 over the cylinder and valve, as shown. Aplurality of spoiler cavities or resonant absorbers 22 are formed in theupper or head wall 14a of piston 14, and as here shown, additionalspoiler cavities 22a may, if desired, be sunk in the upper end portionof the cylinder. Straight spoiler cavities were disclosed and claimed inmy aforesaid patent No. 2,573,536, and functioning and eifect of spoilercavities in combating detonation was there set forth in full. As wasthere explained, such spoiler cavities are effective to absorb soundwave frequencies in the combustion chamber to which they have a resonantresponse; and it will be further understood that the spoilers such asillustrated, formed with closed inner ends, comprise quarter wavelengthpipe resonators having a frequency selective attenuative response tosound waves whose wavelength is four times the depth of the cavities.

The characteristic novel feature of the present invention is that thequarter-wavelength resonant absorbers or spoilers 22 are not straightthroughout their full lengths, but are provided with laterally extendingintermediate sections 23, so that the inner end portions of the cavitiesare laterally offset from the entrance ends thereof. By thisarrangement, the interior end portions of the cavities are substantiallyshielded from the heat produced within the combustion chamber. In thisconnection, it is found in practice that carbon tends to accumulate onsurfaces which are in a certain intermediate heat range, and thatsurfaces maintained at either a relatively high temperature, or at arelatively low temperature, will not accumulate carbon. This is believedto be due to the fact that certain varnishes are produced in thecombustion process. These varnishes are capable of adhering tocombustion chamber Wall surfaces within a certain heat range, soproviding conditions favorable to an accumulation of carbon. Both aboveand below such heat range, the varnishes do not appear on the combustionchamber surfaces and the carbon does not deposit. one means providingoffset shielding from radiation for keeping the inner end portions ofthe resonant cavities at an operation temperature below that for whichcarbon will deposit.

While as stated above, the spoiler cavities shown in Fig. 1 may belocated in either the head wall of the piston, or within the stationarywall structure definitive of the combustion chamber, I have found thatthe piston is in an advantageous location, permitting ready installationof the attenuator configurations without redesign of conventionalcombustion chambers, and operating entirely satisfactorily even thoughthe piston is moving.

Figs. 2 and 3 show another form of acoustic attenuator in the form ofhalf-wave pipe resonators 27 mounted in the piston top 28 (which ofcourse constitutes one wall of the combustion chamber). As shown, thepiston top 28 has cast therein a U-shaped tube 27, whose two open endsopen through the top surface of the piston. The length of this U-tube isone-half the wavelength of the detonation sound wave to be combatted. Ineffect, within its frequency range, the U-tube functions for the purposeherein as two individual quarter-wave pipes. A pressure wave cycle offrequency to which the U-tube is tuned, generated by a detonation originpoint in the flame and incident upon the piston in the region of the twoends of the U-tube, will cause it .to resonate and thereby function as aresonant absorber. In my prior Patent No. 2,573,- 536, I explained theoccurrence of detonation induced resonant sound wave patterns within thecombustion chamber, and the meaning of regions of high acousticimpedance within said patterns. The two ends of the U-tube 27 arepreferably disposed to open to a common high impedance region of such anacoustic pattern. This double, or continuous passage type spoiler isrelatively free of carbon accumulation problems.

Fig. 4 shows a modified piston 31 whose top is formed with cylindricalsockets 32 to receive Helmholtz resonators 33. These resonators eachhave a cylindrical body 34, rounded at the bottom, and formed at theupper end with an external annular flange 3411 which snugly fits thesocket ,32, the body 34 being spaced from the piston structure excepting.at its lower end. Heat conduction to the piston structure is thusreduced, and the resonator operates at a high temperature. At thebottom, body 34 is provided with a stem 34b extending down through thehead of the piston, its lower end being riveted, as at 340, to securethe resonator tightly in position. The resonator is provided with a topwall 34d, furnished with a downwardly extending tubular stem 34s whichopens into the lower portion of body 34, this stem 342 being the neck ofthe resonator. The farthest inner end portion of the cavity of thisresonator, where any carbon might tend to accumulate, will be seen to bethe part which is turned toward the heat to give a condition oftemperature substantially above the aforementioned range where carbonwill deposit, with the result that carbon accumulation within theresonator is minimized or prevented.

Fig. shows another modification of piston mounted Helmholtz resonator,the Helmholtz resonator being formed in this'instance by a bore 35extending upwardly through the top 35a of the piston nearly to the topsurface thereof, and by a smaller bore 35b extending through the topsurface of the piston, the latter forming the neck of the resonator. Thebottom of the bore 35 is then closed by a plug 350, which maybe securedin place by peening as at 35c. The Helmholtz resonator in this form isof advantage in view of its simple nature and the easewith which it maybe formed in a conventional piston structure. Fig. 6 shows still anotherpiston mounted Helmholtz The embodiment of Fig. 1 will be seen to beresonator type of absorber. Here, the piston top 36 is formed with abore 36a extending downwardly from its top surface, and an enlargedcounterbore 36!) extending upwardly from below. The Helmholtz resonatorstructure, indicated generally by numeral 57, includes a cylindricalbase portion 37a, received in counterbore 36b, and secured in positionby peening as at 37 b. Extending upwardly from base portion 37a is acylindrical chamber forming a resonator chamber 370. As shown, the sidewalls of the chamber 370 are annularly spaced from the bore 36a, and thelower ends of the side walls are formed with a series of ports 37d,which ports constitute the mouth of the resonator. Enclosed within thechamber 370 is a steel ball 38. The resonator 37 functions in the usualmanner to attenuate detonation frequency waves of frequency to which itis resonant. The chamber being exposed to the flame, carbon accumulationtherewithin is minimized. In addition, the steel ball 38 is free torattle about inside the chamber owing to the reciprocating motion of thepiston, and this rattling ball has a scouring action on the insidesurfaces of the chamber, tending to prevent carbon accumulation. Inpassing, it may be noted that the attenuator 37 is one of severaldisclosed types which has been arranged in sound transmissivecommunication with the combustion chamber by being positioned virtuallyinside the chamber.

Fig. 7 shows a further piston mounted horn type attenuator, wherein abore 4t), extended downwardly through a body structure .41 of thepiston, receives a plug 4?; formed with a horn-shaped chamber 43. Thethroat of the horn opens through the inner end of the plug 42., asindicated at 4.4, to a groove 45 which communicates with a spiral groove46 formed around the plug 42. The groove 45 and spiral groove .46 form along attenuation passage communicating with the throat of the horn. Thisdevice as illustrated in Fig. 7 forms a convenient and easily madestructure for carrying out the functions of the invention.

Fig. .8 shows a piston whose upper end portion is configured to providea horn type space between it and the cylinder wall, indicated indot-dash lines at 55a. Thus, the top end portion 56 of the pistonconverges in an upward direction on an exponential function curve 57, insuch manner that the cross-sectional area of the annular space betweenthe piston and cylinder wall converges downwardly from the upper end ofthe piston to the plane 58 in the manner of an exponential type horn.This exponential horn passage 5& is reduced to a relatively smalltransverse dimension at the plane 53, something of the order of a fewthousandths of an inch to a millimeter, and there communicates with anacoustic attenuator 6.0 in the nature of a plurality of fine grooves .61formed in the periphery of the piston and arranged to communicate withthe throat of the horn.

It will be seen that detonation sound waves received by the mouth end.of the horn passage or space 59 will travel down the same, Withoutreflection, and will be dis sipated by the attenuator 60. This form ofthe invention is of particular advantage, in that it may be carried intoeffect by a most simple modification of the piston structure. It hasfurther advantage, in that the mouth of the horn 59 is located in theregion of the various pressure anti-node zones of the acoustic patternsknown to exist in the combustion chamber. It is important to note atthis point that it is common to have a taper or stepped diameters,particularly to maintain dimensions in spite of a temperature gradient,for the top portions of pistons. However, unless the taper complies withacoustic laws and includes an attenuative region, the effects spoken ofherein will not be accomplished.

It is of course necessary, as always, to have the passage length, widthand taper and the volume provided by the grooves 61 in proportions whichwill give the necessary frequency band coverage. it is also possible toin.- crease band coverage by increasing the proportion of the r oved 'QElL or t ac p sh t enuati y p op grooves alone, wherein the extendeddistribution of the grooves results in a multi-orifice acoustic baffieoperating as a broad band acoustic wave absorber.

It will be understood that the drawings and description are merelyillustrative of certain specific embodiments of the invention, and thatvarious changes in design, structure and arrangement may be made withoutdeparting from the spirit and scope of the appended claims.

I claim:

I. For use with an internal combustion engine having a combustionchamber and a cylinder opening into said chamber, a piston adapted forreciprocation in said cylinder, and a sound wave conduit in said pistonhaving a half wavelength for the frequency of detonation sound wavesproduced in said chamber by combustion, the two ends of said conduitopening through the top of said piston closely adjacent to one another.

2. For use with an internal combustion engine having a combustionchamber and a cylinder opening into said chamber, a piston adapted forreciprocation in said cylinder, and a sound wave conduit in said pistonhaving a half wavelength for the frequency of detonation sound wavesproduced in said chamber by combustion, the two ends of said conduitopening through the top of said piston into a common region of highacoustic impedance within a resonant acoustic pattern produced in saidcombustion chamber by said detonation sound waves.

3. For use with an internal combustion engine having a cylinder andwalls, including the top wall of a piston, defining a combustion chamberthereover, a sound wave conduit in said walls having a half wavelengthfor the frequency of detonation sound waves produced in said chamber bycombustion, the two ends of said conduit opening into said combustionchamber in close proximiy to one another.

No references cited.

